Acclimating Trim Stock Before Installing

      and use it. April 20, 2008

Can someone please give me the rule of thumb on acclimating wood trim before installing? I am installing standard trim with pine or poplar jambs in two doorways. Is it recommended that I acclimate the wood before installing? And if so, how long? Also, is it okay to stain and poly before I acclimate to the install room? My standard way of doing this in the past has always been to acclimate for a week or two before starting. Thank you for any input.

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor A:
I personally think a week or two would be plenty of time for stock molding. When I first read your post I googled acclimation time and I found the rule of thumb to be anywhere from a week up to six weeks time. What really matters is what environment the wood came out of and where is it going. If you make a drastic change in RH, yes, you need to wait longer, but if the home is a similar environment you should be alright.

From contributor B:
I've read a lot of posts on this site about acclimating material, and what I remember most was that Professor Gene Wengert tends to reply that the material you're installing needs to be around 7% to 8% moisture content (MC), and that's the key. For sure, if you install properly dried wood in a house that has high humidity, there will likely be problems, but acclimating the wood in that situation would be treating the symptom, and not the cause (excessive humidity in the building).

Bottom line: you need a moisture meter, and you need to measure the MC of the material you're installing, and you also need to know if the humidity at the job site is too high (that can be measured with a good hygrometer/humidity gauge). And if you think that's too many hoops to have to jump through, just consider the time and money it will cost figuring out who's fault it is that all the joints have opened up.

From contributor C:
To the original questioner: I just re-read your post. To me, if you stain and poly the trim before it acclimates then it cannot acclimate to the location it will be used in because you will seal it. I would let it sit first then finish and install.

From contributor D:
I agree with all above and would add that it is important to start with acclimating the house. Too many floor installers in my area acclimate the floor for two weeks in the middle summer and the builder has not turned on the A/C. Also, they donít sticker the load so air can not circulate properly. The house needs to be in the same condition in which the people will be living. When acclimated to those conditions, the wood will not move much. The closer the homeowner keeps the house in the range of 65 to 75 degrees and 35 to 45% RH the better, depending on your location.

From the original questioner:
That pretty much confirms my thoughts. To contributor C: I will be staining and poly only front and edges (which I'm sure you know that already) - not the back. Does that not allow the wood to acclimate properly? In the past I have always let the wood acclimate without stain or poly.

From contributor C:
Finishing as you describe will actually make things worse. Sealing one face and allowing the back face to remain raw is not good. Try a flat piece of plywood - stain and poly only one side, set it aside and watch the fun begin.

From contributor A:
Just think of it like wood siding, if you don't prime the back side of the clapboard, paint will peel every other year.

From the original questioner:
I know sealing is important, but did not know that sealing the back was as important as you have described. Are you saying to do as follows: 1. acclimate, 2. stain and poly front and edges, 3. poly the back, 4. install. Also, what if it's going to be painted trim work instead, same process?

From contributor B:
Back priming trim? You guys have to be kidding. For sure, it's a great thing to do, and if you can get paid for it, have at it. I've seen and installed miles of trim that was finished on one side only, and no problems.

The question is acclimating trim. All the back priming in the world isn't going to help if you've got millwork that's at 15% MC. The stuff (backprimed or not), is going to seriously shrink.

Acclimating trim is for *minor* variations on moisture specs. If you have trim that's at 7-8% (which it should be), and it's summertime and the humidity is very high, letting it absorb some moisture is a good idea. But the key is to know what the MC of the wood is. If you don't, everything else you do is guess work, and pales in comparison regarding importance.

If you have a load of wet trim (let's say 15%), and think that acclimating it for a week is going to make any real difference, then I've got a bridge I'd like to sell you. It always amazes me how woodworkers avoid getting a moisture meter. It's the most important tool you can own. The trim is delivered, you measure some random pieces, and 9 times out of ten, the MC is acceptable. That one time when it's 14% is when you call, refuse the material, and make them bring out the right stuff.

Backpriming - for *typical trim work* isn't anywhere near that important. For sure, if you have a wide piece, the rule of thumb is to treat both sides the same (I've seen laminate counters cup like crazy), but for 3-1/2 inch casing, give me a break. For the narrow stock, it's all about MC. For the wide stuff, it's about MC and similar moisture absorption from both sides. To the original questioner: Get a moisture meter and sleep well at night.

From the original questioner:
To contributor B: Thanks. I've installed a fair amount of trim and have only acclimated for a week or two and not sealed the back and have to admit I have never had any problems. I think I will invest in a moisture meter. It just stands to reason, otherwise you are always just guessing. Any suggestions on what models and brands to look at and price range?

From contributor B:
I have an older pin type meter. It works fine, but I'm temped to get one of the pinless types for convenience. As far as what brand, etc., try a WOODWEB search in the upper right corner. There are some past articles I remember reading that talk a lot about the different types of meters.

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